The removal of the pin bones from fillets of salmon is done today, in industrial scale, by hand machines and automatic machines.
However, upon removal of pin bones from fillets of white fish, i.e. cod fishes such as cod, haddock, whiting and saithe, a major problem is the waste arising from the removal of said pin bones and the costs for said removal. This is because the pin bones are removed by a so-called V-cut, which means that the pin bones are cut out. This is done manually with a knife or automatically using rotating blades or by water jet. This means that the fillet becomes completely or partially cut through which generates plenty of waste matter regardless of how the cut is performed, and the fillet is given a less appetizing appearance and the value of the fillet decreases since the pin bones are located at the most valuable part of the fillet.
The difficulty of removing pin bones from fillets of white fish depends upon that the ends of the pin bones are located a bit down towards the abdomen, where the fillet of white fish/cod fishes exhibits a curved surface, and more particularly a concavely shaped surface.
One way to avoid the above problem is to transport the fish to low-wage countries such as China, where the pin bones are removed by hand, and the fillets are then transported to refrigerated display counters of a store. However, this means that the fish or fillet is frozen and thawed several times during the process which impairs its quality. In addition, the long transports have a negative impact on the environment.
By the Swedish patent with publication number SE-467 904 a device is known for removing fish bones, in particular pin bones from fillets of salmon. This known device comprises a housing in which a rotatable driven element is provided. The element is provided with engagement means and has the shape of a cylinder or a truncated cone. The housing has an opening so as to expose a portion of the engagement means of the driven element. Further, there is a resilient abutment which is arranged adjacent and in such a way that a gap is formed between the abutment and the driven element. Upon removal of the fish bones, the fish bones are carried into the gap and clamped between the abutment and the driven element and brought into the housing and discharged through an opening in the housing. A pneumatic disposal unit is connected to the opening.
A disadvantage of this apparatus is that it includes a housing in which fish waste can get stuck and which is difficult to clean. Further, it comprises an expensive and complicated bevel gear.
A further apparatus for particularly removing bones from fish, and more particularly so-called nerve bones or abdominal bones from salmon fillets, is known by the Swedish patent with publication number SE-500 531.
This apparatus differs from the first mentioned apparatus by not include a housing, instead the rotatably driven element is mounted axially on a drive shaft for driving the same. Also this rotatable driven element has the shape of a cylinder.
Both of these apparatuses are intended for the removal of bones, particularly pin bones, from fillets of salmon, but none of them are suitable for removing of pin bones from white fish for reasons stated below.
At a fillet of salmon the ends of the pin bones are located at, when the file is located on a horizontal, flat surface and with the skin side facing said surface, the highest point of the fillet, which means that they are relatively easy to access with the above described apparatuses. Thus, the engagement surface of the rotatably driven element of the prior art has the shape of a cylinder, i.e. the engagement surface of the rotatably driven element forms a straight line which, when removing the pin bones from a fillet of salmon, is parallel with the flat surface of said fillet of salmon.
One difficulty of removing pin bones from fillets of cod fishes is that the ends of pin bones are, when the file is located on a horizontal, flat surface and with the skin side facing said surface, not located at the highest point of the fillet, instead they located a bit down towards the abdomen, where the fillet of cod fishes and many other fish species exhibit a curved surface, and more particularly a concavely shaped surface. This means that the above-mentioned devices for the removal of pin bones from fillets of salmon are not suitable for the removal of pin bones from fillets of cod fishes.
By WO 01/43553 A1 a method and apparatus is known in which the fillets are placed on a conveyor having an upwardly extending edge for elevating a particular area of the fillets and thereby bending the fillets so that the area in which the pin bones are located obtains the highest point above the conveyor and thereby allow the bone removal unit to be brought into contact with said particular area.
Also the engagement surface of the bone removal unit of this application forms a straight line which is parallel with the highest point of the surface of said fillet.
Moreover, since the fillets are bent cracks are possibly formed in the fillets which lower the value of the fillets. It is also difficult to position the fillets on the conveyor so that the ends of pin bones always obtain the highest point above the conveyor.
The above-mentioned Swedish patents have application date 18 Jan. 1991 and 10 Nov. 1992, respectively, and the priority date for the international application is 14 Dec. 1999. Thus, there has been a long felt need for an apparatus for removing pin bones from fillets of white fish.